Direct Evidence of Electronic Interaction at the Atomic-Layer-Deposited MoS₂ Monolayer/SiO₂ Interface

Abstract

The electronic structure of an atomic-layer-deposited MoS 2 monolayer on SiO 2 was investigated using X-ray absorption spectroscopy (XAS) and synchrotron X-ray photoelectron spectroscopy (XPS). The angle-dependent evolution of the XAS spectra and the photon-energy-dependent evolution of the XPS spectra were analyzed in detail using an ab-initio electronic structure simulation. Although similar to the theoretical spectra of an ideal free-standing MoS 2 ML, the experimental spectra exhibit features that are distinct from those of an ideal ML, which can be interpreted as a consequence of S-O van der Waals (vdW) interactions. The strong consensus among the experimental and theoretical spectra suggests that the vdW interactions between MoS 2 and adjacent SiO 2 layers can influence the electronic structure of the system, manifesting a substantial electronic interaction at the MoS 2 -SiO 2 interface.

Advances in Atomic Layer Deposition of Metal Sulfides: From a Precursors Perspective

“…Among the strategies proposed, one of them was to deposit a seed layer of S on SiO 2 to prevent the interaction between Mo and O on the surface, which causes the formation of the buffer layer (Figure 8a) as supposed to be an ideal MoS 2 layer (Figure 8b). However, as reported by Lee et al, 163 there may be parasitic conduction between S and O in a similar ideal free-standing MoS 2 layer as shown in Figure 8c,d.…”

“…The film is grown at 100 °C as opposed to the 300 °C deposition temperature by Tan et al 106 While amorphous, it can be annealed for crystallization. Recently, Lee et al 163 studied the electronic interaction at the interface between SiO 2 surface and MoS 2 deposited by ALD of Mo(CO) 6 and H 2 S. They found that even though SiO 2 is highly insulating, because of the orbital hybridization of the oxygen ions at the interface, the O 2p can contribute to valence as well as conduction bands. This causes a considerable electronic interaction between MoS 2 and SiO 2 .…”

“…(a) ALD reaction causes the formation of buffer layer on SiO 2 and amorphous layer above the buffer, (b) ideal MoS 2 deposition with free-standing layers at the SiO 2 surface (Adapted from Shirazi et al 151 2018; licensed under CC-BY 4.0, https://creativecommons.org/licenses/by/4.0/.) and (c) ideal MoS 2 monolayer on SiO 2 causing (d) orbital configurations causing S−O electronic interactions (Reprinted/adapted with permission from Lee et al163 Copyright 2020 American Chemical Society. ), (e) picture of Au/Si Wafer with 1000 cycles of MoS 2 ALD with (f) SEM images at various locations based on the distance from the gas inlet and (g) their corresponding XRD curves.…”

Self-Assembly of MoS2 Monolayer Sheets by Desulfurization

“…Driven by this fact, various complex self-assembling structural morphologies of MoS 2 monolayer sheets by desulfurization appear. In previous studies, it was found that interesting self-assembling nanostructures can form because of the covalent binding of atropisomeric molecules onto the substrate, indicating the important role of the molecule–molecule and molecule–substrate interactions on self-assembling behaviors. ,,, Interestingly, the physical properties of MoS 2 monolayer sheets may be tuned by the substrates, for example, thermal conductivity and electronic properties. , Due to the different molecule–molecule and molecule–substrate interactions, different substrates may result in different self-assembling morphologies of 2D layered sheets. As is known, a single layer of MoS 2 is composed of S–Mo–S sandwiched structures, and each Mo atom is covalently bonded with six S atoms.…”

Wafer-Scale Growth of a MoS2 Monolayer via One Cycle of Atomic Layer Deposition: An Adsorbate Control Method

“…Since ALD process characteristics are highly suitable for layer-by-layer growth with low-temperature thickness and uniformity control, many research groups have attempted to grow wafer-scale monolayer or few-layer MoS 2 films. − However, none of these studies have been successful for formation of a complete monolayer of MoS 2 using ALD at the wafer scale. Due to steric hindrance and screening effects caused by the surface-adsorbed precursor, the amount of deposited material per one ALD cycle is often smaller than an atomic monolayer .…”